Alumina ceramic substrate is a hard‑brittle electronic ceramic. By adjusting the grade and particle size of white fused alumina powder, the process is divided into two stages: grinding & thinning (coarse‑medium‑fine grinding) and final mirror polishing. Main equipment: double‑side grinding machine, surface grinding machine, CMP (Chemical Mechanical Planarization) machine.
1. Grinding & Thinning Process (material removal and planarization, non‑mirror finish)
Hydro‑classified WA α‑Al₂O₃, also known as corundum / alumina powder.
Technical specifications of white fused alumina powder for alumina ceramic substrate polishing:
Al₂O₃ ≥99.5%, Fe₂O₃ ≤0.03%, Na₂O ≤0.18%.
Hydro‑sedimentation classification is mandatory with strict particle‑size control to avoid edge chipping, micro‑cracks and scratches.
Common grades of white fused alumina powder for alumina ceramic substrate polishing:
Coarse grinding: 320#, 360# — remove CNC tool marks and achieve large‑stock thinning
Medium grinding: 400#, 500#
Semi‑fine grinding: 600#, 700#, 800# — obtain fine matte surface, Ra 0.2‑0.8 μm
2. Final Mirror Polishing (low‑Ra mirror finish after grinding)
Diamond polishing slurry / diamond powder: mainstream high‑end solution. Sequential grain sizes: 1‑3 μm → 0.5 μm → 0.1 μm. Achieves Ra 0.01‑0.05 μm with high material‑removal efficiency but higher cost.
Ultra‑fine white fused alumina powder 2000#‑8000#: mid‑to‑low‑end mirror finish, low‑cost option for semi‑mirror, matte‑high‑gloss surfaces.
Silica sol (colloidal silica) CMP slurry: chemical‑mechanical polishing for nano‑level ultra‑smooth surfaces for high‑end semiconductor substrates. Barely any mechanical damage, yet low removal rate.
Cerium oxide polishing powder: relatively low hardness and weak cutting force on alumina substrates. Rarely used for alumina ceramic substrate polishing; mainly applied for glass and optical lenses.
Process Flow for Alumina Ceramic Substrate Polishing
Cutting → Coarse grinding with 320# white fused alumina → Medium‑fine grinding (400# → 600#) → Fine grinding (800#) → Mirror polishing with diamond / silica sol → Cleaning & inspection